NBA commissioner David Stern has been rattling his saber over the past year when it comes to the practice of flopping in the league. On Wednesday, he finally showed he was serious.

The league released an outline of what will be its new anti-flopping policies.

Its action drew an immediate response from its players' union, which announced Wednesday night if would challenge the rule.

According to policy outline released by the NBA:

“Flopping” will be defined as any physical act that appears to have been intended to cause the referees to call a foul on another player. The primary factor in determining whether a player committed a flop is whether his physical reaction to contact with another player is inconsistent with what would reasonably be expected given the force or direction of the contact.

Physical acts that constitute legitimate basketball plays (such as moving to a spot in order to draw an offensive foul) and minor physical reactions to contact will not be treated as flops.

That means the new flopping guidelines won’t have an impact on in-game result, and there is no review process that would allow referees to stop action, look at tape and change calls. Instead, the league will punish floppers by looking at tape after the game.

The penalties start with a warning and scale upward. After the warning, a second flop gets a player a $5,000 fine. A third is $10,000, a fourth $15,000 and a fifth, $30,000. The league is leaving open what happens to a player after that fifth flop, saying, “He will be subject to discipline that is reasonable under the circumstances, including an increased fine and/or suspension.”

The league said it will announce a separate set of flopping penalties for the playoffs at a later date.

The National Basketball Players Association said it plans to file a grievance and an unfair labor practice challenge with the National Labor Relations Board. Its chief called the rule an "overreaction and overreach" by NBA executives.

In the NBA statement, league vice president Stu Jackson said, “Flops have no place in our game—they either fool referees into calling undeserved fouls or fool fans into thinking the referees missed a foul call. Accordingly, both the Board of Governors and the Competition Committee felt strongly that any player who the league determines, following video review, to have committed a flop should—after a warning—be given an automatic penalty.”

Although there are some defenders around the league known for hitting the floor all too easily on the defensive end, most players are happy about the change. There has been a noticeable rise in flopping over the years, and something needed to be done.

“When I first came into the league, nobody flopped,” said Lakers forward Antawn Jamison, the fourth pick in the 1998 NBA Draft. “Guys tried to see how strong they were and said, ‘You’re not going to knock me down.’ But it has gotten worse. Some guys do it better than others. It will be interesting to see how they call it. It’s tough as a referee what is happening. It will be interesting to see.

“I don’t know how it got to the point it has. You’re starting to see it in big games, in big moments. It has an effect on the game. I think they don’t want it to decide the outcome of a game. I am glad it is happening.”

That puts Jamison at odds with his union.

"The NBA is not permitted to unilaterally impose new economic discipline against the players without first bargaining with the union," NBPA executive director Billy Hunter said in the union's Wednesday statement. "We believe that any monetary penalty for an act of this type is inappropriate and without precedent in our sport or any other sport. We will bring appropriate legal action to challenge what is clearly a vague and arbitrary overreaction and overreach by the commissioner's office."

The NBA's response? "Although we haven't seen any filing from the Players Association, our adoption of an anti-flopping rule is fully consistent with our rights and obligations under the collective bargaining agreement and the law," NBA spokesman Tim Frank said.

However, Jamison was not alone. Lakers star Kobe Bryant said he hopes it has an impact on the game.

"I like the rule," he said. "Shameless flopping, that's a chump move. We're familiar with it. Vlade (Divac) kind of pioneered it in that playoff series against Shaq, and it kind of worked for him."

Players cautioned that it would be difficult to completely eliminate flopping, but welcomed the attempt to try.

"It's good. Guys can't be flopping and get away with it anymore," Oklahoma City Thunder guard James Harden said. "It was bound to happen at some point. Obviously, the league got fed up with it and they put it in. I'm happy they did."